Special numbers in mathematics have composite numbers. A composite number is an integer greater than 1 and can be divisible by other numbers (except 0) except 1 and itself. In contrast, it is a prime number, and 1 is neither a prime number nor a composite number. The smallest composite number is 4. Among them, the perfect number and the number of blind dates are based on this.
One method of composite number is to calculate the number of prime factors. The sum of two prime factors is called semi-prime, and the sum of three prime factors is called wedge number. In some applications, composite numbers can also be divided into composite numbers of odd prime factors and composite numbers of even prime factors. For the latter, where μ is Mobius function and x is half the number of prime factors.